Such goods as are to be transported in ships are nowadays often brought together into standardized load units, usually so called containers, but may also be loaded onto flats having the same base measures as containers and being provided with corner stanchions or foldable gables having a height corresponding to that of a container. The dimensions of a container are standardized internationally, and the use of such units make possible a rapid and rational handling of the cargo. Certain goods, for instance boards and sawn timber may be bundled together to form a unit having the same dimensions as a container, and the expression, standardized load unit, which is used in this specification and the pertaining claims, shall be understood to include also such units, which have the proper dimensions and in which the goods forming the unit are sufficient strong and rigid to permit the handling in the same manner as a container or a flat. Certain moments for instance when loading or unloading a ship, could however be further simplified if several load units could be transported simultaneously.
With ships of the "Ro-Ro" type, namely of the roll-on roll-off type as distinguished from ships handling the units by cranes, etc., fork lift trucks are often used, which have a capacity to lift one, possibly two containers, one on top of the other, for each trip into, or out of the ship. Further advantages could be obtained if a number of standardized load units could be combined to a transportation compound, which by means of a suitable trolley member could be moved into or out of the ship, respectively. In such a manner it would be possible already at the harbour to prepare the cargo into a restricted number of transportation compounds, which could rapidly be brought on board as soon as the corresponding number of compounds had be unloaded.
A container is provided with a built-in box at each of its eight corners for the application of lifting and locking means and furthermore along its lower longitudinal sides with pockets for the fork of the truck. A container is sufficiently rigid to be self supporting between the lower corner boxes. These are, however, so low that it is impossible to use other wheeled lifting means than fork lift trucks, and for practical reasons it is not possible to make the forks so long that two containers, arranged side by side, could be lifted.